#version 330 core

out vec4 FragColor;

in vec3 Normal;
in vec3 FragPos;

uniform vec3 objectColor;
uniform vec3 viewPos;

struct Material {
sampler2D diffuse;
sampler2D specular;
float shininess; //反光度
};

uniform Material material;
in vec2 TexCoords;

struct Light {
vec3 position;
vec3 direction;
float cutOff;
float outerCutOff;

vec3 ambient;
vec3 diffuse;
vec3 specular;

float constant;
float linear;
float quadratic;
};

uniform Light light;

void main()
{
    vec3 lightDir = normalize(light.position - FragPos);
    float theta = dot(lightDir, normalize(-light.direction));
    float epsilon   = light.cutOff - light.outerCutOff;
    float intensity = clamp((theta - light.outerCutOff) / epsilon, 0.0, 1.0);

    // ambient
    vec3 ambient = light.ambient * texture(material.diffuse, TexCoords).rgb;

    // diffuse
    vec3 norm = normalize(Normal);
    float diff = max(dot(norm, lightDir), 0.0);
    vec3 diffuse = light.diffuse * diff * texture(material.diffuse, TexCoords).rgb;

    //specular
    vec3 viewDir = normalize(viewPos - FragPos);
    vec3 reflectDir = reflect(-lightDir, norm);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
    vec3 specular = light.specular * spec * texture(material.specular, TexCoords).rgb;

    // attenuation
    //float distance    = length(light.position - FragPos);
    //float attenuation = 1.0 / (light.constant + light.linear * distance + light.quadratic * (distance * distance));

    diffuse   *= intensity;
    specular *= intensity;

    FragColor = vec4(ambient + diffuse + specular, 1.0);
}
